下颌运动及含种植体口腔生物力学分析

发布时间：2018-12-28 10:22

【摘要】：口腔种植体能显著提高患者的咀嚼功能,且具有类似真牙的舒适感觉,临床上已经被广泛应用于义齿修复。随着口腔种植技术的发展,其生物力学性能成为这一领域的研究热点。有限元法因其具有无创性、计算高效性、模型可重复性、可查看任意结构处应力值等优点,成为该领域重要的研究方法。相关的口腔生物力学有限元研究表明,影响其分析结果准确性的三个关键因素是模型、材料属性和边界条件。由于牙周膜等软组织的提取仍然存在一定难度,因此常规的口腔有限元模型往往忽视了软组织的作用,此外由于下颌运动的复杂性,边界约束条件也常被简化处理,而这些因素都会影响计算结果的准确性。本文建立了含种植体的完整口腔有限元模型,研究了牙周膜与不同边界约束条件对计算结果的影响。采用逆向建模软件从计算机断层扫描图像中提取出完整下颌骨及牙列三维几何模型,利用多边形及曲面处理功能分离出皮质骨、松质骨和完整下牙列,并使用抽壳功能生成了牙周膜及颞下颌关节软组织,从而获得了完整的口腔三维几何模型。此方法获得的几何模型更符合真实的口腔结构,有助于建立有效的含种植体口腔生物力学有限元模型。应用颞下颌关节运动轨迹分析仪,获取了下颌最大垂直开闭口运动时髁突中心的运动数据。髁突中心点运动轨迹表明下颌开闭口运动并不是单一的铰链运动,而是髁突中心点转动与滑动的结合。由数据分析获得的下颌中切点运动轨迹表明下颌骨并不是做刚体运动,以往采用髁突中心点轨迹推导中切点轨迹的方法并不可行。结合下颌运动分析,选取前人研究文献中简化的边界约束条件与本文依据下颌实际运动所建立的边界约束条件,研究其在口腔生物力学中对牙槽骨乃至整个下颌骨应力计算结果的影响。分析结果表明边界约束条件对下颌骨应力分布形式有显著影响,且不同边界约束条件下最大应力值出现在不同区域。在含种植体口腔生物力学模型中,对牙周膜作用的分析发现,有无牙周膜对种植体、牙槽骨及下颌骨上的应力分布形式基本没有影响,但是有牙周膜作用时,种植体骨结合面上最大应力值减小42.96%,牙槽骨上的最大应力值会减小29.03%～52.20%,因此牙周膜能减少从牙齿传递到牙槽骨上的应力;针对边界约束条件的分析结果与不含种植体口腔模型一致,即边界约束条件不仅会影响各组织结构上的应力分布形式,还会影响应力值大小。因此在含种植体口腔生物力学三维有限元建模中应考虑牙周膜组织的作用,并设置更符合下颌实际运动情况的边界约束条件,以提高有限元模型的精确性和计算结果的可靠性。
[Abstract]:Oral implants can improve the masticatory function of the patients significantly and have the comfortable feeling similar to the true teeth, which has been widely used in the clinical application of denture restoration. With the development of dental implant technology, biomechanical properties of dental implant have become a hotspot in this field. Finite element method (FEM) has become an important research method in this field because of its advantages of noninvasive, efficient calculation, repeatability of the model, and the ability to view the stress values of arbitrary structures. The related finite element analysis of oral biomechanics shows that the three key factors affecting the accuracy of the analytical results are the model, material properties and boundary conditions. Because the extraction of periodontal ligament and other soft tissue is still difficult, the traditional oral finite element model often ignores the role of soft tissue, in addition, because of the complexity of mandibular movement, boundary constraints are often simplified. These factors will affect the accuracy of the calculation results. In this paper, a complete oral finite element model with implants is established, and the effects of periodontal ligament and different boundary constraints on the calculation results are studied. Three dimensional geometric models of complete mandible and dentition were extracted from computed tomography images by reverse modeling software. Cortical bone, cancellous bone and complete lower dentition were separated by polygon and curved surface processing. The periodontal ligament and temporomandibular joint soft tissue were generated by the function of exfoliation, and a complete 3D model of oral cavity was obtained. The geometric model obtained by this method is more consistent with the real oral structure and is helpful to establish an effective finite element model of dental biomechanics containing implants. Using the temporomandibular joint motion trajectory analyzer, the movement data of the condyle center during the maximal vertical opening and closing of the mandible were obtained. The movement of the central point of the condyle indicates that the movement of the mandibular opening and closing is not a single hinge motion, but a combination of the rotation of the central point of the condyle and the sliding of the central point of the condyle. The results of data analysis show that the mandible is not rigid body motion, and it is not feasible to use condylar centroid locus to deduce the tangent point trajectory. Combined with the analysis of mandibular movement, the simplified boundary constraint condition in previous literatures and the boundary constraint condition established in this paper according to the actual movement of mandible are selected. To study the effect of the stress of alveolar bone and mandible in oral biomechanics. The results show that the boundary constraint conditions have a significant effect on the distribution of mandibular stress, and the maximum stress values under different boundary constraints appear in different regions. In the dental biomechanical model with implants, it was found that periodontal ligament had no effect on the stress distribution of implant, alveolar bone and mandible, but the periodontal ligament had no effect on the stress distribution of implant, alveolar bone and mandible. The maximum stress on implant bone joint plane decreased 42.96, and the maximum stress value on alveolar bone decreased 29.0352.20, so periodontal ligament can reduce the stress transferred from tooth to alveolar bone. The analytical results of boundary constraint conditions are consistent with the oral model without implants, that is, boundary constraints will not only affect the stress distribution in various tissue structures, but also affect the magnitude of stress values. Therefore, the role of periodontal ligament should be considered in the three-dimensional finite element modeling of dental biomechanics with implants, and the boundary constraint conditions should be set up in order to improve the accuracy of the finite element model and the reliability of the calculation results.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R783;R318.01

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